Hubble's Last Hurrah

Dec. 21, 2007 -- If it is true that what does not kill you makes you stronger, the final incarnation of the Hubble Space Telescope may fundamentally change what is known about existence.

After reversing a decision to cancel a shuttle servicing mission to Hubble, NASA is putting the finishing touches on a flight planned for August to overhaul the world's most popular observatory one last time.

The expectations seem giddily high. Astronomers want to use the refurbished telescope to peer back to when the universe was a mere 460 million years old -- a fraction of its current 13.7 billion years. They plan to hunt down supernova explosions to serve as bookmarks in time and space in an attempt to figure out why the expansion of the universe has sped up in the last 4 to 5 billion years or so.

Some scientists are even putting forth most audacious proposals to chemically analyze the atmospheres of planets circling other stars.

Were it not for Hubble's history, the dreams would be far-fetched. Written off as a boondoggle after scientists discovered its misshaped primary mirror, Hubble, outfitted with corrective optics during the first shuttle servicing mission in December 1993, was resurrected and spent the next 14 years making observations of the universe that drove astronomy textbooks into early retirement.

For example, in an ironic tribute to its namesake, the space telescope uncovered evidence that the universe's expansion is speeding up, not slowing down as predicted. Astronomer Edwin Hubble discovered in the 1920s that the galaxies are all flying apart and that the ones farthest away from Earth are flying the fastest.

"We've been able to use Hubble to probe the story farther back in time," said Adam Riess, a highly regarded 36-year-old astrophysicist at Johns Hopkins University in Baltimore, who developed techniques for using supernova explosions to ferret out the universe's steroid-like expansion rate.

Dark Mysteries

The force whipping the universe's spread has been termed dark energy, which is quite distinct from so-called dark matter.

Watch a slideshow of Hubble's most stunning shots.